A HISTORY OF THE EARTH --DIGGING UP THE PAST

I. ABSTRACT 
Through a variety of multidisciplinary and multisensory activities, students will gain insight into our earth's history. By studying the earth's geologic time, students will discover how animals and plants have evolved and changed over time. In addition, students will learn how scientists use skills of observation coupled with specialized knowledge to make inferences that lead to theory development. Further, each student will actually experience what it is like to be a paleontologist by digging for fossils, recording and weighing their find and making it ready for transport to the museum. By utilizing all their senses, students of all ability levels will be able to understand that history illuminates events and patterns in nature, these events leave their marks for us to examine.

 II. OVERVIEW
Scientists learn about the past in many ways. The evolutionary theory is one way scientists have based their classifications of all living things. It is important to understand the meaning of time and chronology as it relates to this theory. It is also important to realize that the history of the earth can illuminate and help offer theoretical explanations of all events and patterns in nature because these events and patterns leave their marks for us to study.

 III. BACKGROUND KNOWLEDGE

A. Paleontology as a field of study

B. Fossils as a record of the Earth's history and past life forms

C. How fossils are formed, and types of fossils (mold fossil; cast fossil)

D. The ancient age of the earth: the earth's history goes back millions, even billions, of years

E. What is meant by "prehistoric" times

F. Organizing geologic time: Scientists have organized the earth's history into four major eras:

Encyclopedias and other resource books

 V. LESSONS

A. Lesson One: Footprint Puzzle

1. Objective/Goal:

a. Define and compare: observation and inference. Discuss how scientists observe and make inferences to learn about the earth's history, i.e.: reading rocks and studying fossils.

b. Make inferences from "track prints" to understand how scientists "read rocks."

2.Materials

a. Overhead transparency of "Footprint Puzzle" (Figure l)

b. Student graphic organizer (Figure 2)

3.Prior Knowledge for Students

a. None

4.Key Vocabulary 

a. Observation

b. Inference

5.Procedures/Activities

ii. Large tracks

iii. Going same directions

iv. Large tracks get farther apart

Students then list inferences or what they think is happening for Frame 1 on their organizer. Teacher records student responses on board. Discussion follows.

Possible inferences might include:

i. Larger set of tracks may be chasing smaller set of tracks.

ii. Near the edge, the larger set of tracks get farther apart because the creature may be running to catch the small creature.

b. Reveal Frame 2 just as the Frame l was revealed. Students make observations, inferences and recordings as guided by teacher. Possible observations might include:

i. The two sets of tracks meet.

ii. The tracks are all mixed up.

Possible inferences might include:

iii. The two sets of tracks meet because the larger creature attacks the small creature.

iv. The smaller creature struggles for survival.

c. Reveal Frame 3. As in Frame l and Frame 2, the process is repeated. Possible Observations might include:

i. One set of large tracks walks away.

ii. The steps are close together.

Possible inferences might include:

iii. Larger creature eats smaller one.

iv. Larger animal is the parent and carries the smaller one.

a. In discussion, students are able to identify the skills a scientist must use to learn about the earth's history.

  B. Lesson Two (Takes about two class periods) - Reading Rock Layers With Direct Evidence

1. Objective:

a. Review meanings of direct and indirect evidence.

b. Review that the crust is made of many layers that "folded and faulted."

c. Draw the conclusion that the oldest layer of rock is on the bottom.

d. Classify the age of fossils.

2. Materials:

Overhead transparency of rock layers - Figure 3

Copies of Group Worksheets - Assessing Fossils - Figure 4

Crayons, Scissors, construction paper optional

Copies of Individual student worksheets - Figure 5

3. Prior Knowledge:

It would be helpful if students had already studied the geology of the earth. Use the What Every Fourth Grader Need to Know as a resource.

4. Key Vocabulary: Direct evidence (Something that can be directly observed or seen.) 5. Procedures:

1. Focus Question: How can paleontologists find fossils in rock using directevidence?
2. Review with students:
3. Earth's crust is made of many layers and fossils may be found in many different layers. Review difference between direct and indirect evidence in regard to observation/inference activity from Lesson one.
4. Display the diagrams of a cliff on an overhead showing four layers of strata (Figure 3 - part l) Cover part 2.
5. Speculate about what types of rocks each layer could be.
6. Discuss which would be oldest and newest. (Make comparison with clothes hamper - dirtiest clothes on the bottom because they were deposited first.)
7. Display Figure 3 - Part 2 (cover part 1 on the overhead) Distribute Figure 4 for small group activity.
8. Divide class into four groups. Assign each group a different layer. Each group will answer the given questions about its layer only.
9. Each layer group then presents their findings to the class and their conclusions.
10. Using Figure 3, review how scientists can learn much data from fossils and the rock layer in which they are embedded.

1. Tell students to cut out each "rock" and place them together as they would puzzle pieces.
2. Make sure students notice "fossil key" is not in chronological order.
3. Once students have the rock puzzle organized, they then glue the pieces onto the side of the cliff.
4. Using the rock puzzle, students answer the questions on the worksheet.
5. Option: Students may glue the colored puzzle to construction paper if desired.
6. Discuss student answers and show puzzle.

1. Objectives:

a. Learn how scientists can tell how old rocks and fossils are.

b. Learn the meaning of "half-life."

c. Learn the meaning of "carbon 14 dating"

d. Review the concept of "graduated cylinders" if needed.

2. Materials: (For each group of four)

Paper for notetaking, graduated cylinders (preferably long, thin ones)

washable marker (any color)

very soapy water solution - 1/4 cup (made from dishwashing soap)

copies of Soap Suds Activity (Figure 6)

3. Prior Knowledge:

It would be helpful to read the section in What Every Fourth Grader Needs To Know that discusses half-life and carbon dating.

4. Key Vocabulary: half -life and carbon dating

5. Procedures:

a. Focus question: How can scientists judge the age of rocks and fossils?

6. Assessment:

By using the data collected, the students can be lead to infer that molecules in fossils and rocks disappear or escape at a rate that can be calculated by scientists. This allows them to draw inferences and they are able to judge the age of fossils and rocks in the same way suds disappear but return in another form. (The suds disappear, but return in another form. In the same way the molecules {elements} in fossils and rocks disappear {escape} at a rate known to scientists so they can judge the age of fossils and rocks.)

D. Lesson Four - Making a Fossil

1. Objectives:

a. To Learn that geologists and paleontologists study fossils to learn the age of layers of rock.